10 But Amasa took no heed to the sword that was in Joab's hand: so he smote him therewith in the body, and shed out his bowels to the ground, and struck him not again; and he died. And Joab and Abishai his brother pursued after Sheba the son of Bichri. 11 And there stood by him one of Joab's young men, and said, He that favoreth Joab, and he that is for David, let him follow Joab. 12 And Amasa lay wallowing in his blood in the midst of the highway. And when the man saw that all the people stood still, he carried Amasa out of the highway into the field, and cast a garment over him, when he saw that every one that came by him stood still. 13 When he was removed out of the highway, all the people went on after Joab, to pursue after Sheba the son of Bichri.
Matthew Henry's Commentary on 2 Samuel 20:10-13
Commentary on 2 Samuel 20:4-13
(Read 2 Samuel 20:4-13)
Joab barbarously murdered Amasa. The more plot there is in a sin, the worse it is. Joab contentedly sacrificed the interest both of the king and the kingdom to his personal revenge. But one would wonder with what face a murderer could pursue a traitor; and how, under such a load of guilt, he had courage to enter upon danger: his conscience was seared.